AS5040 datasheet(12/28 Pages) AMSCO

12 / 28 page

AS5040 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER

Revision 1.6, 03-Oct-06

www.austriamicrosystems.com

Page 12 of 28

9.3

Zero Position Programming

Zero position programming is an OTP option that

simplifies assembly of a system, as the magnet does not

need to be manually adjusted to the mechanical zero

position. Once the assembly is completed, the

mechanical and electrical zero positions can be matched

by software. Any position within a full turn can be defined

as the permanent new zero/index position.

For zero position programming, the magnet is turned to

the mechanical zero position (e.g. the “off”-position of a

rotary switch) and the actual angular value is read.

This value is written into the OTP register bits Z9:Z0 (see

Figure 13) and programmed as described in section 9.

This new absolute zero position is also the new Index

pulse position for incremental output modes.

Note: The zero position value may also be modified

before programming, e.g. to program an electrical zero

position that is 180° (half turn) from the mechanical zero

position, just add 512 to the value read at the mechanical

zero position and program the new value into the OTP

9.4

Repeated OTP Programming

Although a single AS5040 OTP register bit can be

programmed only once (from 0 to 1), it is possible to

program other, unprogrammed bits in subsequent

programming cycles. However, a bit that has already

been programmed should not be programmed twice.

Therefore it is recommended that bits that are already

programmed are set to “0” during a programming cycle.

9.5

Non-permanent Programming

It is also possible to re-configure the AS5040 in a non-

permanent way by overwriting the OTP register.

This procedure is essentially a “Write Data” sequence

(see

Figure 13) without a subsequent OTP programming cycle.

The “Write Data” sequence may be applied at any time

during normal operation. This configuration remains set

while the power supply voltage is above the power-on

reset level (see 16.5).

See Application Note AN5000-20 for further information.

9.6

Analog Readback Mode

Non-volatile programming (OTP) uses on-chip zener

diodes, which become permanently low resistive when

subjected to a specified reverse current.

The quality of the programming process depends on the

amount of current that is applied during the programming

process (up to 130mA). This current must be provided by

an external voltage source. If this voltage source cannot

provide adequate power, the zener diodes may not be

programmed properly.

In order to verify the quality of the programmed bits, an

analog level can be read for each zener diode, giving an

indication whether this particular bit was properly

programmed or not.

To put the AS5040 in analog readback mode, a digital

sequence must be applied to pins CSn, Prog and CLK as

shown in Figure 16. The digital level for this pin depends

on the supply configuration (3.3V or 5V; see section 11).

The second rising edge on CSn (OutpEN) changes pin

Prog to a digital output and the log. high signal at pin

Prog must be removed to avoid collision of outputs (grey

area in Figure 16).

The following falling slope of CSn changes pin Prog to an

analog output, providing a reference voltage Vref, that

must be saved as a reference for the calculation of the

subsequent programmed and unprogrammed OTP bits.

Following this step, each rising slope of CLK outputs one

bit of data in the reverse order as during programming.

(see Figure 16: Md0-MD1-Div0,Div1-Indx-Z0…Z9, ccw)

During analog readback, the capacitor at pin Prog (see

Figure 15) should be removed to allow a fast readout

rate. . If the capacitor is not removed the analog voltage

will take longer to stabilize due to the additional

capacitance.

The measured analog voltage for each bit must be

subtracted from the previously measured Vref, and the

resulting value gives an indication on the quality of the

programmed bit: a reading of <100mV indicates a

properly programmed bit and a reading of >1V indicates

a properly unprogrammed bit.

A reading between 100mV and 1V indicates a faulty bit,

which may result in an undefined digital value, when the

OTP is read at power-up.

Following the 16th clock (after reading bit “ccw”), the chip

must be reset by disconnecting the power supply.

AS5040 Datasheet(PDF) 12 Page - ams AG

AS5040 Datasheet(HTML) 12 Page - ams AG

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL